Device for securing a balance spring to a balance staff



Nov. 5, 1968 M. DUMONT ETAL 3,408,809

DEVICE FOR SECURING A BALANCE SPRING TO A BALANCE STAFF Filed April 21,1966 2 Sheets-Sheet 1 F'IG.1

NOV. 5, 1968 M. DUMQNT ETAL 3,408,809

DEVICE FOR SECURING A BALANCE SPRING TO A BALANCE STAFF Filed April 21,,1966 2 Sheets-Sheet 2 ELQ LAM United States Patent 3,408,809 DEVICE FORSECURING A BALANCE SPRING TO A BALANCE STAFF Marcel Dumont and GabrielFahudrich, both of Bieuue, Switzerland Filed Apr. 21, 1966, Ser. No.544,147 Claims priority, application Switzerland, Apr. 21, 1965,5,513/65; July 13, 1965, 9,807/65 2 Claims. (Cl. 58-115) ABSTRACT OF THEDISCLOSURE Assembly for securing the inner end of a coiled balancespring to a balance staff, including a pair of spaced, elasticallydeformable plastic securing rings at least one of which is rigidlysecured to the staff, the inner end of the spring being gripped betweenopposing faces of these rings along a length of about one coil and ahalf.

The invention is concerned with a device for securing a watch makersbalance spring to the balance staff.

' In order to secure the balance spring to the balance staff, there isused usually a collet formed by a brass crown driven on the staff. Theinner end of the spring is made rigid with this crown by the gripping ina common hole of its end and of a conical pin, or by gluing 'in a grooveor a slot, which may be spiral shaped. The

In addition to this solution, it has already been proposed to mold thecollet on the inner end of the spring. To this effect, the extremity ofthe spring is introduced in a mold, and one pours therein a low densitymaterial, for example, a plastic material. In this manner, it isrelatively easy to make a plastic collet. It is however necessary toemploy a mold having very exact dimensions and to exactly cen' tre thesesprings with respect to the mold, a very delicate operation. In order toavoid these drawbacks, it has already been suggested to eliminate themolds by pouring the plastic material directly in the centre of thespring in order to form a hub which then can be secured to the balancestaff. This process has the advantage of requiring less precision offabrication than that required for the making of brass collets or ofplastic collets molded in an auxiliary mold. It is no longer necessaryto poise the assembly since the elastic slot has been eliminated, theentire mass deforming itself elastically when the plastic sets andtheplastic material having a relatively low specific Weight, the weight ofthe collet is distributed practically uniformly around the staff.

The present invention has for its object to provide a device forsecuring a watch makers balance spring to the balance staff, whichdevice has all the advantages of a collet molded in the spring, and ismore simplified, the plastic collet embedding the inner coil of thebalance spring being eliminated.

Patented Nov. 5, 1968 According to the invention, the balance spring ismaintained between two elements, the elements bearing on part of alength of the inner end of the blade forming the balance spring, atleast one of said elements being rigid with the balance staff.

According to another characteristic of the invention, at least one ofthe securing elements has guiding means maintaining laterally thebalance spring along at least a part of its length between said securingelements.

Other advantages and characteristics of the invention will appear duringthe description of certain embodiments thereof, given by way ofnon-limiting example, in conjunction with the annexed drawing, wherein:

FIGURE 1 is a cross sectional view of the first embodiment;

FIGURE 2 is a plan view of the device shown on FIGURE 1;

FIGURE 3 is a cross sectional view of a second embodiment;

FIGURE 4 is a cross sectional view of a third embodiment;

FIGURE 5 is a cross sectional view of a fourth embodi ment;

FIGURE 6 is a plan view of the first embodiment;

FIGURE 7 is a cross sectional view taken along line AA of FIGURE 6, andFIGURE 8 is a plan view of a sixth embodiment.

In the securing device shown on FIGURE 1, balance spring 1 is secured bysqueezing between two plastic rings 2 and 3. These two rings areperforated in their centre by a cylindrical hole having a diameterslightly less than the diameter of balance staff 4, so as to makepossible their being driven on this staff. FIGURE 2 shows circularrings, but it may be advantageous to use rings having an outer shapesuch that they determine precisely the setting point of the balancespring to the collet, and that they facilitate the placing into heat ofthe balance springbalance assembly, and furnish a better hold to thetool with which the rings are turned with respect to staff 4, turning atthe same time balance spring 1. The plastic material used for makingthese rings can be either polyethylene, an epoxy resin mixed with ahardener or other similar material. Instead of being driven on staff 4,rings 2 and 3 can also be glued thereon. The pressure exerted by thefaces opposite of rings 2 and 3 on the opposite portion of the part ofthe balance springs compressed between these rings, naturally mustsuffice to prevent all movement of the balance spring with respect tothese rings. The balanec spring is squeezed along approximately one coiland a half. The plastic material forming rings 2 and 3 being elasticallydeformable, the portions of the blade of the balance spring will enterslightly in the opposing faces of these two rings. It is also possibleto glue the balance spring on the faces of the two rings, or to combinegluing and pressure. Preferably ring 3 will have a given thickness andwill bear on the balance or on a shoulder of the balance staff,determining the working height of the spiral for a given caliber.

To secure the balance spring to a given balance staff, it will be enoughthen to select a suitable ring 2 which will be combined with the ring 3of suitable height.

FIGURE 3 shows a second embodiment affording the possibility ofproviding the balance spring connected With its securing device, whichis not the case for the example 3 shown on FIGURE 1. In'this'embodiment,the plastic ring is not directly driven on the stafi, but driven orglued on the end 312 of aplastic bushing 3 the other end of which has ashoulder 3a forming the other gripping elements for balance spring 1,the securing of the balance spring between ring 2 and shoulder 3a takingplace in the same manner as in the example of FIGURE 1. The height ofshoulder 3a determines the working height of balance spring 1 withrespect to the balance. In this example, it suffices to drive or to gluebush 3 on the balance staff. The outer surface 3b of bush 3 need notnecessarily be cylindrical but can on the contrary have a surface suchas to prevent all angular movement of ring 2 with respect to theshoulder 3a.

Ring 2 can have a form such as to facilitate the putting into beat ofthe assembly and to determine precisely the setting point of the balancespring to the collet. The device naturally can be mounted in a positionturned around by 180 with respect to the position shown in FIGURE 3, theheight of surface 3b determining then the working height of the balancespring 1. Shoulder 3a preferably will have a shape such as to facilitatethe putting into beat of the assembly by moving angularly bush 3 withrespect to balance staff 4.

Since the principle of operation of the device consists in squeezing thebalance spring between two opposite parallel faces, it follows that oneof these surfaces can be made with the balance spring.

FIGURE 4 shows such an embodiment in which the balance staff has ashoulder 4a made integrally therewith, balance spring 1 being secured bya bush terminating in a drum 2a pressing on the balance spring. Thislatter device naturally affords great stability to the balance springowing to the rigidity of the metallic shoulder 4a and the large contactsurface between the bush and the staff 4.

Utilisation of a plastic material of course makes possible the use ofrings of various colours.

The rings can be insulating, or may be made electrically conductive byadding thereto metallic powders or by metallising their surfaces so asto use them in electromechanical watches.

The rings and the bushes can be made of thermo-plastic resins orthermo-setting resins, with or without a hardener.

Before securing the balance spring between the two clamping faces, thespring is centered by means of a suitable device. Such a device canconsist in a fitting having a plate with a housing intended to receivethe lower securing ring, and centering pins disposed around the housingand able to engage between two consecutive turns of the spring to centerthe same.

Said housing can also be made in the bottom of a second housing havingan inner diameter arranged within the inner diameter of the firsthousing, the second housing or bed being provided with a very thin wallinterrupted in at least one place, so as to permit the partial insertionof the main spring into its barrel by means of a main spring winder, thewalls of this second housing or bed introducing itself between twoconsecutive turns of the spring.

The described securing devices permit, in spite of their greatsimplicity, to provide an assembly sufliciently secure of the balancespring to the balance staff, the horizontal stability of the balancespring being very great owing to the fact that at least one turn of thebalance spring is rigidly maintained.

In the securing device shown on FIGURE 5, the balance spring 1 ismaintained between two rings 12 and 13 driven on staff 4 as describedabove. The lower ring has a spiral shaped groove 13 in which is placedwithout stress balance spring 1. The balance spring being guided andlaterally held by the groove, ring 12 need now only ensure its axialposition, and owing to this fact, the pressure exerted on the portionsof the main spring on the two securing rings can be kept down to a verylow value; all the more since groove 13 can have a suificient depth toguide the spring along the greater part of its height. The depth of thegroove must not exceed the height of the balance spring. With respect tothe materials which can be used to make these rings, it is possible touse either metal or plastic or any other material as long as theconditions required by the invention are fulfilled.

FIGURES 6 .and 7 represent another embodiment, the essential features ofwhich correspond to those represented on FIGURE 3. We find again a ring12 made for example of plastic material which is not directly driven onthe staff, but driven or glued on to the end 1312 of a bush 13 the otherend of which has a shoulder 13a forming the other securing element. Thisshoulder 13a additionally has three rows of heads 13c, 13d and 13egrouped in pairs and uniformly distributed in spiral configurationaround the staff of the device. The distance separating the two heads ofeach pair is such that the balance spring can be introduced withoutstress between said heads. The spiral on which are distributed the pairsof heads correspond exactly to the balance spring coil free of allstress.

In the embodiment shown on FIGURE 8, the guiding elements are formed bythree studs 13g, 13h and 13i spirally distributed around the staff ofthe device, and the diameter of the studs being equal to the distancebetween two consecutive coils of the spring. These studs are disposed insuch a way that they can introduce themselves between the turns of thebalance spring without stressing the same. These studs preferably in anumber greater than three, can be grouped in rows in the same manner .asthe heads in FIGURE 6.

In the embodiment shown on FIGURES 6, 7 and 8, the guiding elementspreferably are made integrally with element 13 and can be greater than3. Additionally, the two securing rings can be provided with the saidguiding elements.

Returning to the embodiment shown on FIGURE 4, it is also possible tocombine one ring, made for example in plastic, with a shoulder madeintegrally with the staff, the guiding means, whether it be a groove,heads or cylindrical studs, which can be provided either on the plasticring or on the metallic shoulder of the staff.

In all the examples described above, guiding means made of a sufficientheight, suffice practically to secure the balance spring. But sincethese guiding means are provided for cooperating with the securingrings, it is sufiicient to provide guiding elements which bear on onlyone face of the spring blade. For example, instead of pairs of headsshown on FIGURES 6 and 7, it will suffice to only provide outer lugs.

Accordingly, many variations are possible both in the form, number ofthe guiding elements and in the choice of materials used.

What is claimed is:

1. Assembly for securing the inner end of a coiled balance spring to abalance staff comprising a pair of spaced, elastically deformable,securing rings fitting around said staff, at least one of said ringsbeing rigidly secured to said staff, said inner end of said spring beinggripped between opposing faces of said rings to a length of about onecoil and a half, at least one of said rings having guiding means forholding said spring laterally for at least that part of its length lyingbetween said rings, said guiding means consisting of spirally disposedpairs of upstanding lugs provided on one of said rings around saidstaff, each lug of said pairs being spaced by a distance slightly inexcess of the thickness of said spring.

2. Assembly for securing the inner end of a coiled balance spring for abalance staff comprising a pair of spaced, elastically deformable,securing rings fitting around said staff, at least one of said ringsbeing rigidly secured to said staff, said inner end of said spring beinggripped between opposing faces of said rings along a length of about onecoil and a half, at least one of said rings having guiding means forholding said spring laterally for at least that part of its length lyingbetween said rings, said guiding means consisting of upstanding studsspirally disposed on one of said rings around said staff, the size ofsaid studs not exceeding the distance between two consecutive coils ofsaid spring.

References Cited UNITED STATES PATENTS 438,672 10/1890 Banta 58-115975,697 11/1910 Lange 58-115 2,329,710 9/1943 Fix 58115 6 2,419,1034/1947 Whitehead 58-115 2,842,935 7/1958 Bradley 58--115 FOREIGN PATENTS373,698 1/ 1964 Switzerland.

RICHARD B. WILKINSON, Primary Examiner.

S. A. WAL, Assistant Examiner.

